Circulatory support during coronary bypass surgery, heart transplantation, or after failed coronary angioplasty is currently achieved using cardiopulmonary bypass. This involves the complete support of the heart and lungs by diverting all the blood returning to the heart through a pump and oxygenator, before returning it to the arterial circulation. During coronary artery bypass grafting or heart transplantation, cannulation for cardiopulmonary bypass is done at surgery through the chest, whereas cardiopulmonary bypass for failed coronary angioplasty can be done percutaneously through the groin in the cardiac catherization lab. Regardless of the circumstances or route of cannulation, cardiopulmonary bypass has a time limitation of three to four hours due to the continued trauma to formed blood elements such as platelets and red blood cells. This is primarily due to the oxygenator in the circuit. The patient must undergo full anticoagulation with heparin prior to cardiopulmonary bypass and the bypass circuit must be assembled and run by a certified perfusionist.
Circulatory support before and after surgery may be required for several days. Usually the lungs and right ventricle are functioning adequately and only the left ventricle requires extended support. The employment of left ventricular assist allows extended circulatory support without the blood trauma of cardiopulmonary bypass or the services of a perfusionist and requires only partial anticoagulation.
Left ventricular assist requires the drainage of blood from the left atrium of the heart which is currently done by cannulation of the left atrium at the time of surgery. In 1962, an alternative method called "transseptal left atrial cannulation" was proposed by Dennis et al.. in "Left Atrial Cannulation without Thoracotomy for Total Left Heart Bypass", Aca. Chir. Scand. 123: 267-279, 1962 using a metal cannula directed down the right jugular vein. The cannula was directed across the interatrial septum and drained left atrial blood without the need for thoracotomy. More recently, Glassman et al. in "A method of closed-chest cannulation of the left atrium for left atrial-femoral artery bypass", The Journal of Thoracic and Cardiovascular Surgery, Vol. 69, No. 2, February 1975 has advocated transseptal left atrial cannulation by the right femoral vein. These publications describe hardware and procedures which are too complex and awkward for widespread clinical acceptance.
U.S. Pat. No. 4,790,825 issued to Bernstein et al. illustrates one proposed method of transseptal left atrial cannulation based largely on work with the Glassman group. In Bernstein, first a guide wire protruding through a catheter is inserted into the femoral vein and directs the catheter up the veins to the right atrium. Second, the guide wire is withdrawn from the entire length of the catheter and a needle is directed up the entire length of the catheter and protrudes out the end. The needle pierces the interatrial septum and the catheter is advanced over the needle into the left atrium. Third, the needle is removed from the entire length of the catheter and an obturator (with a circular barb for attaching to the catheter hub) is directed up the entire length of the catheter. Fourth, an external obturator extension is screwed on to the internal obturator. Fifth, a cannula is threaded over the entire length of the catheter and obturator with the tip positioned in the left atrium. Finally, the catheter and the obturator are removed from the interior of the cannula. A thoracotomy is not required for insertion or removal of the left atrial cannula.